"The device's pulse is painless," said study team member Yousef Mohammad, an associate professor of neurology at Ohio State University. "The patients have felt a little pressure, but that's all."

The researchers recently created a portable version of their device.

In the brain

Migraines are estimated to affect some 28 million Americans and are three times more common in women than in men.

Migraines are typically more severe than common headaches and originate in the brain, Mohammad explained in a telephone interview. So-called "tension" headaches, in contrast, are the result of stress in the muscles of the head and face.

Scientists still aren't sure what causes migraines, although a recent study linked them to low levels of a chemical called serotonin in the brain. That study also found that migraine sufferers report higher levels of sexual desire than people with tension headaches.

TMS devices were originally developed in the 1980s and many are currently awaiting FDA approval for the treatment of psychological disorders such as depression and auditory hallucinations.

The researchers plan to test their device in a larger, 200-person study.